Clunk / Rattle Right Rear Suspension

[TheMegalodon]

Wanted to revive this old thread and see how some of the posters cars are doing months later. I installed BMR minimum drop performance springs and Koni Active shocks a couple months back. Nothing else added. Had the bushings indexed and an alignment done, everything in spec. Car rode well and had no noise until a month ago. Installed my winter wheels and shortly after I started getting the EXACT noise that Must_Tang described in his original post. A small rattle from the rear right over multiple small high frequency bumps. A mechanic buddy and myself jacked up the car and put it on ramps to check a few things. I know sometimes the rear shock mounts can be a problem. Mine are stock. My left rear wheel bearing had also failed so I had that replaced under warranty at the dealer thinking that was the issue.

With a new wheel bearing in place, right side’s wheel bearing is good, I still get the rattle noise. I have to assume it’s the rear toe links, maybe the outer toe bearing as some have mentioned.

I have a 2015 performance pack GT. Would changing out to the FRPP toe link bearings potentially fix this? I know it’s a nasty install so I wanted to ask first.

This god damn IRS rear is elusive when rattles and stuff show up. These cars certainly aren’t that smooth to begin with over bumps in the rear. The Koni Actives have been decent with a lot less suspension travel and better rebound but rear ride comfort is about the same as stock, compliant but not comfortable (especially highway).

Thanks for any insights.

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[Nerass]

long story short, replaced my entire rear subframe with another 15k mile take off.
only aftermarket parts on this, bmr drag springs, viking shocks, and cb005. no other suspension components were loosened
i have the same rattle i did prior to switching my cradle.

 

[TheMegalodon]

long story short, replaced my entire rear subframe with another 15k mile take off.
only aftermarket parts on this, bmr drag springs, viking shocks, and cb005. no other suspension components were loosened
i have the same rattle i did prior to switching my cradle.

So are we to believe that it could be an issue with the IRS accepting aftermarket springs/shocks?
I checked my springs are properly perched, I didn’t get any play in my toe rods when I checked. It’s going to the dealer today cause I’m at a loss.

 

[TheMegalodon]

Update: took the car to my dealer. Their suspension tech did a full shake down of the car and checked everything. Rear strut top nuts had loosened up and it was likely a result of the bump stops not giving my shocks enough clearance. Even though I cut them down enough according to the instructions for the BMR springs, the shocks had little more than a finger width of travel before hitting the bump stops. Trimmed them back more, tightened up the nuts and the car is riding smoother than before with no nasty noises. Couldn’t be happier.

UPDATE 2 - November 20th: After a couple days of driving on my city’s garbage roads, the noise has returned but much softer than before. It’s tolerable but I’m so confused as to what could still be causing this. I don’t know if I should trim the rear bump stops more or what. Everything else on the suspension is torqued to spec, exhaust isn’t rattling, nothing in the trunk is causing this. So damn weird.

The front suspension has zero issues.

 

[Nerass]

i don't run any bumpstops, ill check the tightness of my upper nut.. i transferred the entire shock assembly over to the new one.

 

[TheMegalodon]

It was the rear shocks. I swapped out the garbage Koni Actives (with only 2k miles) for Bilsteins. Problem solved. Before that I put in Eibach bump stops and J&M rear shock mounts to help improve the situation.

 

[LoneWolf97]

https://www.mustang6g.com/forums/th...-trunk-rattling-buzzing-vibration-fix.187213/

I just posted my same experience and solved it!

 

[TheMegalodon]

That’s a great suspension setup. Hope it helps! I still have a rear rattle that may be worn bushing related. I’m going to also check the tightness of the rear shock mount top nuts. Rear suspension manages bumps well but over repeated small bumps I have noise on both sides. Need to investigate.

 

[konjiki7]

It was the rear shocks. I swapped out the garbage Koni Actives (with only 2k miles) for Bilsteins. Problem solved. Before that I put in Eibach bump stops and J&M rear shock mounts to help improve the situation.

I think my Koni Active specials are doing the same thing... had them on the car for 6 months w/ 5k on them. They now ride like a fairly tight Coilover....

 

[TheMegalodon]

It was the rear shocks. I swapped out the garbage Koni Actives (with only 2k miles) for Bilsteins. Problem solved. Before that I put in Eibach bump stops and J&M rear shock mounts to help improve the situation.

Just bought some steel OEM style rear shock mounts from Rock auto and replaced the J&M worn ones (with spherical bearings). Noise is completely gone. Note to self: don’t be foolish and buy anything with spherical bearings on a car that’s driven in winter. Car feels fantastic now without the awful metal rattle noise even though it rides similar. I had the shop trim the rear eibach bump stops half an inch as well to give more shock travel. My car can now glide over these crappy streets with grace and zero rattles.

All my bushings are in great shape still. Car only has 70k miles (107k kms).

 

[DarkOni]

Just bought some steel OEM style rear shock mounts from Rock auto and replaced the J&M worn ones (with spherical bearings). Noise is completely gone. Note to self: don’t be foolish and buy anything with spherical bearings on a car that’s driven in winter. Car feels fantastic now without the awful metal rattle noise even though it rides similar. I had the shop trim the rear eibach bump stops half an inch as well to give more shock travel. My car can now glide over these crappy streets with grace and zero rattles.

All my bushings are in great shape still. Car only has 70k miles (107k kms).

Hey, late reply but wonder if anyone can help. I have a somewhat similar issue. I have coilovers and i do understand they are to be rough, but from my engineering background, i know the small impacts i hit on the road should not be enought to cause such noises in the rear. I also have the J&M mount and the shocks i have have way less travel than stock fixed length. I did the math for motion ratio and it helped a lot. But i have a feeling these Mounts have enough clearance to make then rattle loud on any small bumps. However, i also think i need to replace the shocks with similar oem shaft travel. Did your belisteins have said similar lenght or were they shorter ? Also, has the steel type mount held up well? Thanks

 

[S550HPP]

I think my Koni Active specials are doing the same thing... had them on the car for 6 months w/ 5k on them. They now ride like a fairly tight Coilover....

What's the date stamp on yours? I had 2019/20 and they were defective have 2024/25 incoming now. No hassle warranty with online seller thankfully don't have to pay shipping return or return at all.

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